Buffon's Needle Experiment (BNE) is a classic problem of geometric probability, where one drops a needle randomly onto a region of evenly spaced parallel lines. This app simulates a simple case where the needle's length is the distance between two adjacent parallel lines. Let N be the total number of needles dropped at a certain moment; let C be the number of needles crossing lines. Let R = 2 × N ÷ C. R is an approximation of Pi ( π). In this app, the user can change the number of needles dropped at each time and the number of lines across the target region. Please be advised that the method converges very very slowly due to nature of the problem.